[Changes in the cardiac and "sleep--wakefulness" cycle rhythms following isoproterenol administration to white rats]

The heart-rate during sleep-wakefulness cycle did not significantly change after isoproterenol administration. However, both the duration of R--R intervals and their dispersion became sharply increased. The observed shifts were least obvious during the slow-wave sleep. The bradycardia periods during paradoxical sleep in rats are supposed to be a beneficiary background for further suppresion of the sinus automatism up to sinoauricular blockade. The data obtained suggest that the heart-rate during wakefulness can be a reliable enough evidence of its oscillations in other phases of the cycle. The revealed changes of the sleep structure involved increasing part of paradoxical stages in the total time of sleep in animals when measuring it starting from the 5th day after the sympathomimetic administration.